In 2018 we released experimental support for multiple devices: http://blog.leapmotion.com/multiple-devices/
An experimental installer and Unity examples may be found here: https://github.com/leapmotion/UnityModules/tree/feat-multi-device/Multidevice%20Service
For information about how to activate multi-device support in Unity, see this forum thread: https://forums.leapmotion.com/t/multiple-devices-on-getting-frames-from-one-device/7578/3
However, it’s important to note that support for multiple devices does not mean auto-magic support for tracking the same hands from multiple positions. It is possible, but requires a highly advanced set of heuristics to outline under which conditions the software should (1) decide that a hand seen from one device is the same as a hand seen from another device, (2) know when a hand ID should persist from one field of view to another, and (3) how to prioritize conflicting reports of different hand elements, and present the results accordingly. You also have to know with absolute precision where each controller is in the space in relation to the others, which would involve a lot of manual calibration.
This represents a non-trivial project that would make sense in some extreme edge cases (like an LBE that wants to supplement the hand tracking at a certain point during the experience, or a manufacturer that wants to embed multiple controllers for a physical installation), but for the most part is a non-starter.